Is Noise Bad

In London today the sun set at 16:36. Between then and dusk at 17:15 there is still enough natural light for the human eye to see features in the scene and do most activities.

Compared to the human eye, however, cameras have a much more compressed range of being able to detect all the gradations from dark to light.

I shot this at 16:59, so fifteen minutes before dusk.

You have two choices if you want to photograph in this low light – increase the ISO or keep the camera at base ISO and put it on a tripod.

I shot this at ISO 6400 and f3.2 and 1/200th of a second. If I had put the camera on a tripod I would have had to use a slow shutter speed. At base ISO I would have had to shoot at 1/4th of a second and the person coming out of the station would have been a blur.

So what are the downsides of ISO 6400 in poor light?

The photo is very noisy. Look at the close-up of the face of the man in the shadows.

So then you might think noise is a terrible thing. But at a normal viewing distance the photo will look OK. It is only when we get close that we see the noise.

Of course if I were to print it and stare at it at the same distance as I am from the computer screen then I would see the noise. But if the print was in a frame and hung on a wall, the a normal viewing distance might be more than two metres (a bit over two yards) and you would hardly see the noise.